Appendix 3 Modbus™ Register Map And Application Notes - Novatech 1635 User Manual

MODBUS™ REGISTER MAP AND APPLICATION NOTES
Modbus Functions Supported are:-
ReadHolding Register Function 3
WriteHolding Register Function 6 ( for allowable addresses only )
Introduction.
The 1635 Analyser implements a subset of the modbus slave protocol, it is intended to work in conjunction with a
modbus master.
This is accomplished by setting the Modbus address to some non-zero value in the range 1-31, setting the jumper
positions to select the RS485 half duplex configuration, and re-starting the analyser.
The master must be configured as follows:-
Baud Rate
Parity
Stop Bits
RS485
Mode
A typical transaction would be to read the current value of a variable from the analyser.
The master send a ReadHoldingRegister packet, with the appropriate address and the analyser responds with data at that
address.
The Register Addresses are as follows, to convert to Schneider addresses for earlier model PLC's address space, add
40001 to each address.
For later model PLC's with linear address space the address co-responds directly to %MW XXXX address.
For Example, to read dryer absolute humidity 1 -
Read %MW2064 which is equivalent to holding register 42065 = 40001 + 2064
Some data is 32 bit data (double) which requires some care to ensure that the word order is correctly interpreted.
For Example, OXYGEN32, (dual probe) which is at address 2052 is interpreted as follows.
2052 contains the high 16 bits for probe 1 oxygen
2053 contains the low 16 bits for probe 1 oxygen
2054 contains the high 16 bits for probe 2 oxygen
2055 contains the low 16 bits for probe 2 oxygen
August 2009
1635 Water Vapour Analyser
APPENDIX 3
9600
None
1
Half Duplex
RTU ( binary mode)
61